This invention relates to a transfer-type electromagnetic relay and to a method of manufacturing a relay support for use in supporting the transfer-type electromagnetic relay.
As disclosed in U.S. Pat. No. 4,342,016 issued to K. Yokoo et al. and assigned to the instant assignee, a conventional transfer-type electromagnetic relay of the type described comprises a housing and a contact assembly housed in the housing. The contact assembly comprises an armature swingable around an axis of swing placed on an armature lead to carry out contact transfer, a leaf spring carried on the armature, and a pair of movable contact studs attached to both ends of the leaf spring. A pair of fixed contact leads with fixed contact studs in the housing, are extended from the housing outwards. The fixed contact studs are selectively brought into contact with movable contact studs, respectively. Moreover, a permanent magnet is placed on the fixed contact lead to urge the armature towards a predetermined one of the fixed contact studs when the relay is deenergized. As a result, each permanent magnet must inevitably be placed axially outwardly of the fixed contact stud on the lead and be laterally spaced apart from the fixed contact stud. This means that a magnetic path becomes long between the permanent magnet and an end of the fixed contact lead which contacts with an armature. Thus, magnetization is weakened between the fixed and the movable contact studs. As a result, a large size or strong permanent magnet must be accomodated in the housing in order to compensate for the weakening of the magnetization. Accordingly, the conventional transfer-type relay is rendered bulky.
A pair of arm members are attached in the conventional transfer-type electromagnetic relay to the leaf spring along the leaf spring to reliably urge the armature towards the predetermined fixed contact stud when the relay is deenergized. For this purpose, each of the arm members is directed towards the same direction as the other. In this structure, stiffness of a pair of the arm members is varied in both cases where the armature is swung towards one of the fixed contact studs and where it is swung towards the other.
Each of the armature lead and the fixed contact leads is supported by a relay support serving as a part of the housing and is helpful to form a part of a magnetic path. Therefore, each lead is preferably made of a magnetic metal. In this event, magnetic interference is unavoidable between the armature lead and each fixed contact lead. In addition, it becomes difficult to manufacture the relay support with a high reliability and quality and further with a reduction in size of the relay.
Another conventional transfer-type electromagnetic relay comprises make-before-break contacts which are concurrently and momentarily closed on transferring the contacts from one to another. In this event, a card is indispensable so as to drive leaf springs to which a pair of movable contact studs are attached. Therefore, the conventional relay inevitably becomes complicated in structure.